The liver plays a vital role in carbohydrate metabolism and regulation of blood glucose. The following statement(s) is/are true concerning carbohydrate metabolism by the liver

a. Glycogen, a complex polymer of glucose, is synthesized by the hepatocyte in a remarkably energy efficient process

Serum glucose is tightly regulated by the liver despite wide fluctuations in dietary ingestion. The liver can take up as much as 100 g/day of glucose and convert it to glycogen by the process of glycogenesis. The liver can also release glucose into the blood by glycogenolysis, the breakdown of glycogen, or by gluconeogenesis, the formation of new glucose from substrates such as alanine, lactate, glycerol or dietary amino acids. Hormones play a key role in hepatic regulation of glucose metabolism. Insulin, for example, stimulates glycogenesis, and glucagon stimulates glycogenolysis and gluconeogenesis. Gluconeogenesis is also enhanced by fasting, critical illness and periods of anaerobic metabolism

Glycogen is a complex polymer of glucose. Liver cells can store up to 8% of their weight as glycogen. The first step in glycogen storage is the transport of glucose through the hepatocyte plasma membrane. About 90% of portal venous glucose is removed from the blood by liver cells through carrier-facilitated diffusion. The rate of glucose transport is enhanced by insulin. Once in the hepatocyte, glucose and ATP are converted by the enzyme glucokinase to glucose-6- phosphate (G6P), the first intermediate in the synthesis of glycogen. Because complete oxidation of one molecule of G6P generates 37 molecules of ATP, and storage only uses one molecule of ATP, the overall efficiency of glucose storage in glycogen is a remarkable 97%. Glycolysis is the pathway by which glucose is converted to two molecules of pyruvate and occurs in the cytoplasm in contrast to the citric acid cycle which occurs in the mitochondria.